The world’s governments reached a global agreement at the Climate Conference in Paris to cap global warming at 2 degrees Celsius (4 degrees Fahrenheit), but the effort may be up against a big hurdle: mathematics.

As per analysis by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, even if countries adhere to the Paris climate agreement hammered out last fall, capping global warming at 2 degrees Celsius (4 degrees Fahrenheit) would likely require net zero greenhouse gas emissions by 2085 and actually negative carbon emissions over the long term. More than 100 participants to the Paris Agreement committed to cut greenhouse gas emissions by 2025 or 2030.

Even if all the countries follow through on their commitments, steeper cuts would be necessary after 2030 and by the end of the century, total emissions would need to become negative, meaning more greenhouse gases would be removed from the air than are emitted into the atmosphere to stay below 2 degrees Celsius..

“The emissions targets in the Paris Agreement are an important first step, and it’s known that additional action will be required to meet the goal of limiting warming to 2 degrees,” said NCAR scientist Benjamin Sanderson, lead author of the study. “This paper provides details of what the next steps would need to look like in order to actually hit that target.”

This graph represents eight possible pathways that society could take to have a two-in-three chance of limiting warming to 2 degrees Celsius. The blue line represents our current emissions trajectory. The red line represents the path that society will be on if countries adhere to the Paris Agreement. The gray lines represent other possibilities, all of which require more stringent emissions cuts in the near term but fewer negative emissions later.

Responsibility for the Future

Even before the Paris agreement was finished, it was clear that the pledged emissions cuts by 2030 would not be sufficient on their own to meet the target of limiting warming to 2 degrees.

“We created a wide range of possible global emissions pathways that would allow us to have a decent shot at limiting warming to two degrees,” Sanderson said. “We found that very small increases in the rate at which we cut greenhouse gases now could lead to very large decreases in the amount of negative emissions we need later.”

Negative emissions in the future will require the massive deployment of technologies that are still hypothetical to draw down greenhouse gases from the atmosphere. To make this world a better place, we would require near-term cuts that are much more aggressive than those proposed in the Paris agreement.